I. Field of the Invention
The present invention generally relates to the field of actuators for four bar linkages and, in particular, the present invention is concerned with actuators for translating the linkage of an articulating frame press from a first position to a second position.
II. Description of the Prior Art
Linear actuators for translating a four bar linkage from one position to another as applied in presses are known. U.S. Pat. Nos. 3,154,009; 3,651,754; and 3,641,929 disclose a linear actuator for translating the motion of a press with an articulating frame from one position to another. These devices all employ a press frame that has opposed links or legs of equal length and the legs remain parallel to their opposed legs throughout the translation of the press frame from one position to another. This parallelogram configuration makes it relatively simple to attach one end of a linear actuator such as a cylinder to the base and another end of the cylinder to a link of the frame and actuate the frame from one position to another with a continuous linear motion of the actuator. My invention U.S. Pat. No. 4,329,867 discloses an articulating frame press which comprises a four bar linkage having legs of unequal length. In U.S. Pat. No. 4,329,867 a rotary actuator was disclosed for translating the press from a first position to a second position. To articulate the press or translate from a first position to a second position utilizing a rotary actuator such as a rack and pinon or hydraulic motor it is necessary that the rotary actuator reverse its motion at a point between the first position and the second position because the rotary motion of the legs relative to the base is reversed during the translation. This requires a sophisticated control for the rotary actuator so that at a precise position of the frame the motion of the rotary actuator is reversed. This adds complication and expense. In the present invention a linear actuator is interconnected between opposing links of a four bar linkage so that when one link has reversed its motion and is rotating toward the opposed link, the opposed link is continuing its rotation toward the one link at a sufficient rate to exceed the rate of rotation of the one link and allow actuation of the four bar linkage with a continuous motion of the linear actuator.
III. Information Disclosure Statement
The aforementioned prior art including the applicant's U.S. Pat. No. 4,329,867 in the opinion of the applicant and the applicant's attorney, represents the closest prior art and/or information of which the applicant and his attorney are aware.